////: 



-, tx. 



203 



2. The origin of lite stemo-kyoid muscle. 



3. The origin of the stemo-tkyroid muscle. 



4. The origin and insertion of tlic triangularis stcrni. 



5. The costal anil sternal origins of tlie tUaf>liragm. 



6. The parietal layer of the pleura, through which you can see the muscles. 



7. The internal mammary artery ami reins, on each side of the sternum, 

 giving off their anterior intercostal and other arteries. (Fig. 143.) 



Dissection. Cut through the ribs in the mid-axillary line. (Fig. 145.) Cut 

 through the abdominal walls along the margin of the false ribs. Cut through 



P H R K.VIC XKRVK 



,tn nrt'iij 

 vein, cut 



A nterior intercostal branch 



Anterior intercostal branch 



Mtixculo-phrenic artery 



circumjlex iliac artery - 



(\iiiiiiinii rnuiliil artery 



Internal jitijnlnr if in 

 Sulirl Hi-inn i-fin. cut 

 Sooleuua anticus muaole 



STERNUM 



TrianRulariB Bterni niuacle 

 Perforating branch 



Superior epigastric artery 



Deep epigastric artery 



FIG. 143. SCHEME OF THE INTERNAL MAMMARY ARTERY. 



the diaphragm close to the ribs and sternum. Then elevate from below 

 the section of thoracic wall you have made loose. As you turn this section up 

 you will sec a large amount of anterior mediastinal connective tissue behind the 

 sternum. Klevate the section slowly; let an assistant divide the connective 

 tissue, and do not injure the numerous structures that enter or leave the apex 

 of the thorax. 



Figure 141 shows the infracostales. These muscles arise near the angle of 

 the ribs, from the inner surface and lower border ; they are inserted into the 

 second rib above. They are also called subcostals. 



